Cant stop crying, my dog is gone

I've had to put down my dog today, his health went downhill and the vet said he doesn't want to do this, but there's nothing else left to do and Bruno is struggling (I saw that). Ive been crying for 3 hours now I can't stop. He was 13 years old and I got him in my first year of highschool. He was always cheerful and sassy, until the last few months. Heres a picture of Bruno.